Abstract: OBJECTIVE To investigate the effects of osthole on peak bone mass of rats. METHODS Twenty-four one-month SD rats were randomly divided into two groups, one group was orally administrated osthole at 10 mg·kg^-1 and the other was given equal volume of distilled water and used as the control. The body weight was monitored every week and the bone mineral density(BMD) of total body was measured every month. All rats were sacrificed after three months. The femoral bone mineral density, the serum levels of osteocalcin(OC) and anti-tartaric acid phosphatase 5b (TRACP 5b) were measured. The bone microarchitecture was analyzed with μCT and the bone biomechanics properties were tested with universal material machine. RESULTS No significant differences were observed between osthole-treated group and the control for the food-intake and body weight during three months. However, the rats treated with osthole had significant higher BMD for both total body and femoral than the control. The osthole-treated rats also had higher level of serum OC and lower level of TRACP 5b. Besides, they owned bigger bone volume/tissue volume, trabecular thickness, trabecular number but smaller trabecular spacing and structural model index. In the three point bending tests of femurs, they were found to have larger maximum load and the young’s modulus and yield load. CONCLUSION Orally administered osthole can enhance peak bone mass by improving bone formation and inhibiling bone resorption, and therefore can be used to prevent osteoprosis.